Apparatus for supporting a shaving tool in an adjustable tool holder for multiple gauge strip draw shaving

ABSTRACT

An improved method and apparatus for supporting the shaving tool in an adjustable tool holder for use in the production of multiple gauge strip is disclosed wherein the adjustable tool holder is vertically positioned on gauge blocks and thereby rigidly supported against the strip to be shaved by applying a vertical load on the adjustable tool holder.

BACKGROUND OF THE INVENTION

The invention relates to a method and apparatus for the preparation ofmultiple gauge metal strip by a shaving operation wherein the strip isdrawn through the shaving apparatus over an arced surface.

It is necessary to provide a multiple gauge thickness in a metal stripin many applications such as the production of copper strip for theformation of electrical conductors and the like. Conventional proceduressuch as continuous milling have been employed to produce the desiredvariations in gauge, however, such processes suffer from thedisadvantages of being both time consuming as well as generating anunfavorable form of scrap.

An additional procedure which has been known in the art to producemultiple gauge metal strip comprises the reduction to gauge by a rollingoperation. However, the rolling operation in the production of multiplegauge strip has been found to suffer from the disadvantages of beingrestricted to certain shapes, and furthermore tend to involve complexand costly tooling. Additionally, it has been found that the productproduced by the aforesaid rolling process fails to meet commercialtolerances as well as being free from other structural defects.

A further method of producing multiple gauge metal strip is by a drawingprocess. However, certain complications resulted from this process. Inthe normal drawing process reduction of the thickness in a sectionresults in an increase in section length so that if the thickness of agiven shape varies across its width, the drawing process will result invariable changes in length causing non-uniform metal flow and stressesleading to buckling, twisting, tearing and fracture of the workpiece.Though a wide variety of drawing techniques are known, including theemployment of the hydrodynamic principle, none have been suggested orwould appear to alleviate the aforenoted deficiencies associated withthe drawing of complex multiple gauge configurations.

The technique of shaving as a form of metal reduction has been known inthe art for some time. However, its application has been generallylimited to the finishing of materials of uniform cross section by thereduction of the cross sectional area of the workpiece, with thereduction being conducted along the entire surface thereof. Thistechnique is illustrated in U.S. Pat. No. 3,055,102 to Shaw et al.wherein a shaving tool is applied against a rod or bar which reduces thecross sectional area along the entire surface thereof.

Certain problems would appear to arise if this shaving techniqueexemplified by Shaw et al. were to be directly applied to the productionof multiple gauge strip products from rectangular stock. Specifically,the application of shaving force against only a portion of the totolsurface of the strip tends to magnify the problems set forth in theaforenoted patent, particularly, the inability to hold the workpieceproperly centered with respect to the tool with the result that theworkpiece wanders and a wavy or broken surface may result. A furtherdifficulty which would arise and be magnified by the removal of stockfrom only a portion of the workpiece surface would be the excessivechattering that takes place as the strip would pass through the toolwhich would appear on the finished product as a torn or galled surface.

One known method of producing multiple gauge strip by draw shaving isillustrated in U.S. Pat. No. 3,992,977 to Winter et al. and assigned tothe assignee of the present invention and incorporated herein byreference. The method and apparatus for producing multiple gauge metalstrip in the aforesaid U.S. Patent while found to be superior topreviously known methods still was found to suffer from deficiencies.More particularly, the rake angle at which the tool was disposed wasfound to be limited to a range of 21/2° to about 25° and was preferablyabout 5° to 18°. Any increase in rake angle above those critical valueswould cause the workpiece to ride up the tool resulting in excessivestrip material being removed. Thus, as a result of the limit on rakeangle, the amount of volume removed per pass was also limited.Furthermore, the manner in which the tool was held in position withrespect to the anvil and strip was found to produce chatter marks on theshaved portion of the multiple strip product not unlike those chattermarks encountered in the aforesaid machining operations. The chattermarks are undesirable for functional reasons as well as cosmeticreasons. Chatter marks on the metal strip impedes the bonding ofsemi-conductor chips to the strip as well as inhibiting the metalplating of the strip which may be necessary in the production ofelectrical conductors and the like. The shaved gauge variation of thestrip was found to be ±0.002" while variations in the transversepositioning of the cut groove were 0.005". Finally, the finishedmultiple gauge strip product was observed to have significant scratchingon the backside thereof as a result of being drawn over the flat anvilduring the shaving process. Furthermore, the shape of the final productexhibited an increase in cross-wise dish with a corresponding increasein cut depth and/or width. This cross-wise dish can be attributed to theinsufficient hold-down forces of the strip against the flat anvil.

SUMMARY OF THE INVENTION

In accordance with the present invention, it has been found that ashaving operation for the production of multiple gauge strip productsmay be conducted wherein the strip is drawn through the shavingapparatus over an arced surface thereby allowing an increase in rakeangle while at the same time minimizing cross-wise dish in the finalproduct. The improved apparatus of the present invention includes animproved support structure for rigidly fixing the cutting tool'sposition with respect to the arced surface and strip thereby improvingshaved gauge tolerances while reducing chatter marks.

The features of the present invention comprise the provision of an arcedsurface of polished carbide which eliminates backside scratches andthereby not only improves the cosmetic qualities of the multiple gaugestrip product but also reduces the shaving stresses. The employment ofan arced surface allows the tool's rake angle to be increased to a rangeof from 20° to about 45° thereby resulting in a corresponding decreasein relative shaving stress. Since the shaving stress is directly relatedto the volume of material which can be removed per pass withoutexceeding the yield strength of the material, the increase in rake angleallows greater volume removal per pass. Furthermore, with an arcedsurface, the strip can be caused to wrap around the surface therebyproviding effective hold-down of the strip against the surface, thisability to wrap around the surface results in a reduction in cross-wisedish. By providing strip guides on the arced surface, the widthvariations of the shaved surface are improved.

A further feature of this invention contemplates an improved supportcomponent for rigidly fixing the tool's position with respect to thearced surface and strip thereby eliminating chatter marks whileimproving gauge depth tolerances.

The method of this invention possesses certain advantages overconventional milling procedures in that scrap retrieval is made easieras the removed stock is usually obtained in the form of a longcontinuous coil whereas the scrap generated by conventional milling isin discontinuous chips of random shapes and sizes. The method of thepresent invention also exhibits advantages over previously known drawshaving processes for multiple gauge strip in that the tolerances of theshaved surface are improved, cross-wise dish is minimized, backsidescratching is greatly eliminated, and by the increase in allowable rakeangle of the tool the volume of material capable of being removed perpass is greatly increased.

It is, accordingly, a principal object of the present invention toproduce an improved method for the manufacture of multiple gauge metalstrip products which employs an improved shaving operation.

It is another object of the present invention to provide a method andapparatus as aforesaid which will increase the volume of metal removalper pass.

It is a further object of the present invention to provide an apparatusfor the performance of the shaving method as aforesaid which improvesthe tolerances obtained in the shaved surface of the multiple gaugemetal strip.

Still another object of the present invention is to produce a multiplegauge metal strip in which chatter marks are greatly reduced.

Other objects and advantages will become apparent by those skilled inthe art from a consideration of the description which proceeds withreference to the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a shaving apparatus employed inaccordance with the invention;

FIG. 2 is a side view of the apparatus shown in FIG. 1;

FIG. 3 is a sectional view taken along line 3--3 in FIG. 1; and

FIG. 4 is a partial side view of a further embodiment of shavingapparatus used in accordance with the invention.

DETAILED DESCRIPTION

In accordance with the present invention, the foregoing objects andadvantages are readily obtained.

Shaving is a metal removal process akin to machining or broaching, andutilizes a stationary cutting tool and a moving workpiece. As in anycutting operation, such variables as speed, tool geometry, stock removaland lubrication are important, however, unlike most metal cutting, theamount of stock removal achieved in a shaving operation is controlled bythe maximum force which can be exerted on the strip before yieldingoccurs. Essentially, this is the same kind of restraint imposed on awire drawing operation. The limiting force is, therefore, equal to theyield strength of the strip multiplied by the strip cross sectional areaafter shaving. This may be expressed as follows:

    F.sub.max =Y.S.(A.sub.F)

where,

F_(max) is the limited force;

Y.S. is the yield strength; and

A_(F) is the strip cross sectional area after shaving.

Another relationship observed is that the force required to remove agiven cross sectional area of strip by a shaving operation is equal tothe cross sectional area of the shaving cut multiplied by a machining orshaving constant, C. This relationship may be expressed as an equationwhich, when solved for C, is as follows:

    C=F/A.sub.r

Where,

F is the drawing force;

A_(r) is the cross sectional area removed by shaving; and

C is the shaving constant.

It has been found in accordance with this invention that the successfulpreparation of multiple gauge strip may be accomplished by a shavingoperation if the maximum amount of metal removal per shaving pass isdetermined in relation to the yield strength of the strip and theshaving constant, C, determined above. This relationship is inferredfrom the observation that, as the drawing force is increased, a maximumforce is ultimately reached which corresponds to the yield strength ofthe strip. Thus, at this point F=F_(max), and, by substitution thefollowing expression is derived: ##EQU1## Where,

A_(o) is the initial cross sectional area of the strip;

A_(r) is the cross sectional area removed by shaving;

C is the shaving constant; and

Y.S. is the yield strength of the strip.

Thus, by the above equation the maximum stock removal per pass byshaving may be calculated by determining the shaving constant and theyield strength of the strip. The shaving constant can be calculated fromexperimental measurements of drawing force which may then be substitutedinto the expression C=F/A_(r), set forth earlier. The yield strength ofthe strip is determined by normal tensile testing methods such as the0.2% offset yield strength method which was used herein.

Upon determining the maximum stock removal in accordance with theprocedures set forth above, the shaving apparatus can then be adjustedso as not to exceed the maximum value. Such an adjustment will, ofcourse, vary with the nature of the apparatus employed. For example, inthe present invention, the apparatus for adjusting tool depth comprisesan upside down U-shaped housing which is positioned on readilyreplaceable gauge blocks. Adjustment of tool depth is made by employingvarious size gauge blocks.

Another conventional parameter which influences the successful practiceof the shaving method of this invention is the determination of theshaving tool rake angle. The rake angle is defined as the angle whichthe plane of the vertical leading surface of the tool defines withrespect to the imaginary vertical plane perpendicular to the directionof strip travel. In cutting operations such as the method of thisinvention, it is usually found that a certain critical rake angle existswhich, if exceeded, results in a loss of control of the thickness of thefinished workpiece. Usually, a rake angle in excess of the criticalvalue causes the workpiece to ride up the tool, with the result thatexcessive stock is removed.

The shaving apparatus employed in accordance with the present inventioncomprises an adjustable shaving tool provided with a cutting edgedefining a pattern corresponding to the multiple gauge surface desiredin the final strip product. The shaving tool is horizontally andvertically adjustable to enable shaving to be conducted to successfullyachieve maximum possible strip reductions measured primarily in terms ofvolume removal. As noted above, maximum volume removal per shaving passmay be generally determined in relation to the yield strength of thestrip and then coordinated with the cross sectional configuration of thedesired end product. This being done, the apparatus is thenappropriately adjusted to achieve the extent of volume removal desired.The various embodiments of the apparatus employed in the presentinvention will be described in greater detail hereinbelow.

Referring to FIG. 1, a shaving apparatus used in accordance with thepresent invention is illustrated in perspective. The apparatus 10comprises a shaving tool 12 located adjacent and on a metal strip 14which is being drawn across arced anvil 16. The cutting edge 18 of theshaving tool 12 contacts strip 14 at the top region of anvil 16, asshown in the drawings, and defines a cutting pattern whose configurationserves as the template for the final configuration of the multiple gaugestrip product. Attached to the arced anvil 16 for guiding the metalstrip 14 are a pair of strip guides 22 which are symmetricallypositioned about the center line of the polygauge strip and spaced apartfrom each other the width of strip 14. The guides 22 are securely fixedto the anvil 16 by means of bolts 24 or other suitable means. The stripguides should be manufactured of a wear resistant material such as highspeed tool steel so as to limit wear which may occur because of therelative motion between the strip 14 and the guides 22. The arced anvil16 may be provided with a polished carbide insert 26 under the contactarea of the tool which is secured by bolts 28 as well as by strip guides22. The carbide insert may be secured to the anvil by other means suchas brazing, adhesives or the like. Alternately, the arced anvil itselfcould be made of polished carbide. The radius of curvature of the arcedanvil is limited on the high side by the ability to get the desireddownward tensile force while minimizing total contact length and on thelow side by the tendency to plastically deform the strip as it is drawnin tension over the anvil. It has been found that a radius of curvaturefrom about 1 to about 12" is satisfactory, preferably from about 2 to8".

As shown in FIG. 1, the shaving tool 12 is supported by and secured toan adjustable tool holder 30 comprising tool support structure 32 whichis secured to vertically adjustable housing 34. Housing 34 is an upsidedown U-shaped structure comprising vertical legs 36 which are integralwith connecting horizontal member 38. Shaving tool 12 is secured in themanner shown by support structure 32 which in turn is integral with theU-shaped housing 34 so as to allow the entire adjustable tool holderassembly 30 to move vertically as a whole. The adjustable tool holderassembly 30 is adapted for horizontal and vertical movement on tracks 40and 41 in any convenient manner known in the prior art for example, ascrew travel slide connection, a sliding jack arrangement, by manualmeans, or any other suitable means. The adjustable tool holder assembly30 rests on gauge blocks 42 which are readily capable of being replacedby gauge blocks of varying thicknesses. The tool holder assembly 30 isheld in its appropriate vertical position against the gauge blocks 42 byproviding an appropriate vertical load on the horizontal member 38. Thisvertical load may be in the form of simple weights or alternatelyhydraulic, pneumatic, or other suitable means for insuring that theassembly remains rigidly fixed with respect to the anvil and strip. Asis clear, fine adjustments of the vertical position can be made byreplacing the gauge blocks with other gauge blocks of suitabledimensions.

As stated above, maximum stock removal is determined with respect to theyield strength of the strip and the particular configuration desired. Inaddition to the aforenoted adjustments of the vertical position of theshaving tool, a further critical adjustment is made which relates to therake angle of the tool edge. The rake angle is defined as the anglewhich the plane of the vertical leading surface of the tool defines withrespect to the imaginary vertical plane perpendicular to the directionof strip travel. In accordance with the present invention, it has beenfound that the critical rake angle at which the cutting tool may bedisposed is greatly increased over that of U.S. Pat. No. 3,992,977. Therake angle found to be useful in the aforesaid U.S. patent was fromabout 21/2° to about 25° and preferably from about 5° to about 18°. Inthe present invention, it has been found that as a result of theemployment of an arced anvil, a rake angle as high as 45° may beemployed without causing the strip to ride up the cutting tool. Thisincrease in rake angle is attributed to an increase in effectivehold-down of the strip against the anvil as a result of the anvil beingarced which causes the strip to wrap around said anvil. In addition, theemployment of bridle rolls (not shown) ahead of and behind the arcedanvil surface may also be used to thereby provide additional hold-downforces of the strip against the anvil. Increasing the tool's rake anglefrom the previously defined range, as indicated in U.S. Pat. No.3,992,977, to that range which is capable of being attained in thepresent invention results in a reduced shaving stress and improved stripcosmetics. The improvement in the shaved surface finish results from thefact that an increase in rake angle results in a corresponding decreaseof the built-up material adjacent to the tool's face. Increasing therake angle also results in substantial reductions in shaving stress andconsequently, a greater amount of material can be removed per pass thanwas previously possible.

The improved adjustable tool holder assembly results in improved shavedgauge tolerances over those realized in aforesaid U.S. Pat. No.3,992,977, as a result of the use of a vertically loaded tool holderagainst precision machined gauge blocks and rigidly fixing the positionof the anvil, strip and tool with respect to each other by applying saidvertical load. The shaved gauge variation was reduced from ±0.002", asstated in the aforesaid patent, to ±0.0005". In addition, the employmentof strip guides on the anvil has allowed variations in the transversepositioning of the cut groove to be reduced from 0.005" to 0.001". Inaddition, providing a polished carbide anvil or insert therefor,backside scratches of the polygauge strip were substantially reducedfrom that of the previously known method while correspondingly effectinga reduction in shaving stress.

The totality of the modifications of the present invention, i.e.,increasing tool rigidity, providing an arced anvil, strip guides, andpolished carbide inserts, results in improved surface finish of theshaved portion, reduced backside scratching, elimination of chattermarks on the shaved portion, and improved shaving efficiencies byallowing a greater removal of material per pass.

While the above shaving apparatus has been employed with an arced anvil16 (FIGS. 1 and 2), it should be appreciated that a freely rotatingwheel 46 (FIG. 4) may be substituted for the arced anvil and stilleffect the improvements of the present invention. In addition, theemployment of a freely rotating wheel would tend to reduce frictionalcontact between the metal strip and the corresponding arced surface.Again, bridle rolls ahead of and trailing the rotating wheel will allowthe strip to more effectively wrap around the wheel and thereby providebetter hold-down of the strip thereon.

The following example is presented in order to gain a fullerunderstanding of the method and apparatus of this invention and toillustrate the advantages obtained therefrom. The example is presentedfor the purpose of illustration only and should not be construed as alimitation on the invention.

Five samples of 1/8 hard CDA Alloy 128 where prepared for draw shaving.An apparatus was employed for the draw shaving which comprised a shavingtool in accordance with the present invention. The alloy samplescomprised flat ribbons of strip measuring 0.906" by 0.080". The 0.2%yield strength of the material was 22 ksi while the ultimate tensilestrength was 36 ksi. The cutting tool width was 0.062" and the tool wasset to cut a shaving depth of 0.007". Five samples were shaved inaccordance with the present invention with the cutting tool set at arake angle varying from 8° to 44°. The radius of the arced anvil was 3".The drawing force, F, was measured for each test and the relativeshaving stress was calculated using the aforenoted formula. The resultsof the experiment are set forth below in Table I.

                  TABLE I                                                         ______________________________________                                        Rake Angle (Degrees)                                                                         Relative Shaving Stress (ksi)                                  ______________________________________                                         8             1200                                                           20             850                                                            28             650                                                            36             450                                                            44             400                                                            ______________________________________                                    

Based on the data in Table I, and the mathematical relationship betweenpercent stock removed and shaving stress, it can be seen that a productfabricated with three passes using an 8° rake angle tool would onlyrequire one pass if the rake angle of the tool was set at 44°. As notedpreviously, this effective increase in allowable rake angle is directlyattributed to the excellent hold-down force on the strip which occurs asthe result of the employment of an arced surface over which the strippasses.

It is to be understood that the invention is not limited to theillustrations described and shown herein, which are deemed to be merelyillustrative of the best modes of carrying out the invention, and whichare susceptible of modification of form, size, arrangement of parts anddetails of operation. The invention rather is intended to encompass allsuch modifications which are within its spirit and scope as defined bythe claims.

What is claimed is:
 1. Apparatus for the production of multigauge stripmaterial comprising a tool holder assembly, said tool holder assemblyincluding a horizontal member having speed vertical legs dependingtherefrom, a shaving tool having an elongated cutting edge, said shavingtool being located between said legs and being supported by said toolholder assembly, a base, an anvil having an arced surface supported onsaid base, said tool holder assembly being supported on said base andsaid shaving tool being located opposed to and adjacent the arcedsurface of said anvil, means for vertically adjusting and maintainingsaid tool holder assembly at a predetermined height to provide a desiredshaving gap between the cutting edge of said shaving tool and the arcedsurface of said anvil, whereby a predetermined gauge of metal strip canbe shaved from a thicker strip drawn between the anvil and the shavingtool.
 2. Apparatus according to claim 1 wherein said arced surface isstationary.
 3. Apparatus according to claim 1 wherein said arced surfaceis rotatable.
 4. Apparatus according to claim 1 wherein said anvil has asurface of carbide.
 5. Apparatus according to claim 1 wherein said arcedanvil has strip guides secured thereto.
 6. Apparatus according to claim1 wherein said tool has a rake angle of about 21/2° to about 45°. 7.Apparatus according to claim 1 wherein said adjusting and maintainingmeans include at least one gauge block of selected height seated betweeneach leg of said assembly and said base.
 8. Apparatus according to claim7 wherein said adjusting and maintaining means include means forapplying a vertical downward force to the assembly.
 9. Apparatusaccording to claim 8 wherein the vertical force is caused by fluidpressure means.